The high-definition multimedia interface (HDMI™) is a licensable compact audio/video connector interface for transmitting uncompressed digital streams. The HDMI connects digital audio/video (or multimedia) sources (e.g., a set-top box, a DVD player, a personal computer, a video game console, etc.) to a compatible digital audio device and/or video monitor such as a digital television. In contrast to consumer analog standards the HDMI enforces digital rights management (DRM) on transmitted media. The HDMI is fully described in the HDMI™ Specification version 1.3 published on Jun. 22, 2006, incorporated herein by reference in its entirety merely for the useful understanding of the background of the invention.
A block diagram of a HDMI link 100 is shown in FIG. 1. A multimedia source 110 transmits high speed data using transition minimized differential signaling (TMDS®) characters. The TMDS characters encapsulate video, audio, and auxiliary data and are carried over three TMDS channels 130-1, 130-2, and 130-3. TMDS characters are transported at three different time periods: a video data period, a data island period, and a control period. During the video data period, the pixels of an active video line are transmitted. During the data island period, which occurs during the horizontal and vertical blanking intervals, audio and auxiliary data are transmitted within a series of packets. Control codes are transported during the control period, which occurs between video and data island periods. The control codes include, for example, encryption status signals (ESS), HSYNC signals, VSYNC signals, and delimiters. A multimedia sink 120 receives the TMDS characters and converts them into digital video streams, data packets, ESS, HSYNC and VSYNC signals.
A clock, typically running at the video pixel rate, is transmitted on a clock channel 140 and is used by the multimedia sink 120 as a frequency reference for data recovery on the three TMDS channels 130. In addition, configuration, system-level control, management and status information is exchanged between the multimedia source 110 and the multimedia sink 120. The system-level control includes display data channel (DDC) and consumer electronics control (CEC) which are transmitted over channels: SCL 150, SDA 160, and CEC 170. The DDC is used for exchanging configuration and status information between the multimedia source 110 and sink 120. The CEC protocol provides high-level control functions between all of the various audiovisual products in a user's environment. The SDA 160 and CEC 170 are bidirectional channels, while the SCL 150 is unidirectional channel (from source 110 to sink 120). A standard HDMI interface further includes a hot-plug detect (HPD) signal 180 which originates at the sink 120.
As can be noticed, at least eight channels are required to implement the HDMI link 100, where each channel is a twisted-pair wire. Typically, the multimedia source 110 and multimedia sink 120 are physically coupled using an HDMI cable that is designed to channel at least the signals 130 through 180. The HDMI standard defines different categories of HDMI cables, each of which has a different purpose and a unique connector type. The performance of a typical HDMI cable is usually a function of its length. For example, high quality cables can reach, at most, up to 15 meters. Another disadvantage of standard HDMI cables is their cost. Typically, such cables are significantly more expensive than other cabling standards, e.g., coaxial and RCA cabling.
Some prior art approaches utilize a dual category 5 (Cat-5) cable to replace a standard HDMI cable. The price of a Cat-5 cable is a fraction of what retailers charge for an HDMI cable. Cat-5 is a twisted pair cable type designed for high signal integrity. This type of cable is often used in structured cabling for computer networks (e.g., Ethernet) and many other signals such as basic voice services. A Cat-5 cable includes four twisted pairs in a single cable jacket. This use of balanced lines helps preserve a high signal-to-noise ratio despite interference from both external sources and other pairs.
However, to implement an HDMI interface, two Cat-5 cables are required to channel signals 130 through 180. This is a limiting factor, as connection through two Cat-5 cables is generally undesired for aesthetic reasons and/or installation convenience and cost compared to a single Cat-5 cable. Furthermore, as in many structures, every room is wired using only a single Cat-5 cable (and RJ-45 connectors). Thus, it would be desirable to have transmission of HDMI signals from a multimedia source to a multimedia sink over a single Cat-5 cable.